More than two years after Boeing acknowledged problems with the 747-8’s flight management computer (FMC), the airplane carrying a package of improvements largely centered on the Honeywell FMC took to the air last week. Taking off from Paine Field in Everett, Washington, at 1:30 p.m. local time on May 20, the 747-8 Intercontinental flew for about four hours with the newly upgraded FMC and a performance improvement package (PIP) for its General Electric GEnx-2B turbofans.
Some six months before Boeing delivered the first 747-8 freighter in October 2011, then-program chief Elizabeth Lund conceded that the new FMC’s capabilities no more than matched those of its predecessor on the 747-400. Meant to provide more memory and faster processing, the new computer promised ATC efficiency features such as quiet climb, optimal wind trade step and required navigation performance. However, those capabilities won’t appear in revenue service until late in the year, said Boeing. In February customers received an integrated display system update, which improved the display and messages for the environmental control system, flight controls and hydraulics, and enabled the airport moving map. Honeywell declined requests to explain the prolonged problems with the FMC’s performance, as it has done since Boeing first confirmed the computer’s shortcomings in 2011.
While Boeing and Honeywell ironed out the kinks in the FMC, GE devised and inserted the GEnx-2B’s performance improvement package (PIP), certification testing of which the engine company expects to finish “soon.” According to the engine maker, the GEnx-2B PIP combines the best features from the two PIPs designed for the Boeing 787’s GEnx-1B. The -2B PIP includes a new low-pressure turbine design and improvements to the compressor, combustor and high-pressure turbine. GE promises the changes will effect a 1.6-percent improvement in fuel efficiency and meet the original specification. Boeing quotes a 1.8-percent improvement as a result of the engine and FMC modifications combined.
Finally, Boeing expects the test program to validate design changes related to the 747-8I’s horizontal stabilizer fuel tank system, disabled before first delivery to Lufthansa because of its tendency to cause a flutter condition under certain structural failure scenarios. The tank carries some 3,300 gallons of fuel, allowing for a range increase of some 300 nm in a VIP-configured 747-8I.